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Justyn W. Regini, J. Günter Grossmann, Peter Timmins, John J. Harding, Andrew J. Quantock, Stuart A. Hodson, Gerald F. Elliott; X-Ray- and Neutron-Scattering Studies of α-Crystallin and Evidence That the Target Protein Sits in the Fenestrations of the α-Crystallin Shell. Invest. Ophthalmol. Vis. Sci. 2007;48(6):2695-2700. doi: 10.1167/iovs.06-0559.
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purpose. α-Crystallin, a ubiquitous molecular chaperone, is found in high concentrations in the lens. Its structure and precise mechanism of action, however, are unknown. The purpose of these experiments was to further the understanding of the chaperone function of α-crystallin.
methods. X-ray- and neutron-solution-scattering studies were used to measure the radius of gyration of bovine lens α-crystallin when complexed with its target protein β-crystallin in both normal and heavy-water-based solutions. Spectrophotometry was used as a chaperone assay.
results. The radius of gyration of α-crystallin on its own and when mixed with β-crystallin was 69 ± 1 Å at 35°C and increased with the temperature. In contrast to H2O-buffered solutions, the radius of gyration did not increase significantly in D2O-buffered solutions up to 55°C, and at 70°C was, on average, some 15 to 20 Å smaller.
conclusions. Bovine lens α-crystallin in solution can be modeled as a fenestrated spherical shell of diameter 169 Å. At physiological temperatures, a weak interaction between α- and β-crystallin occurs, and β-crystallin is located in the fenestrations. Deuterium substitution indicates that the superaggregation process is controlled by hydrogen bonding. However, the chaperone process and superaggregation appear not to be linked.
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